Field of the Invention
The present invention relates to an image forming apparatus, an image forming method and a computer readable medium.
Description of Related Art
Traditionally, there has been image forming apparatuses which form a pattern image for colourimetry on a sheet, change the image forming condition and the like in accordance with the read value obtained by a colorimeter (colourimetry unit) provided in the apparatus reading the pattern image and carry out color adjustment of the apparatus (for example, see JP 2014-170195).
In the traditional image forming apparatus, the colorimeter provided in the apparatus is a simple version and its reading accuracy is low. Therefore, in the case where the absolute density of an image is to be adjusted, the pattern image is to be read by a colorimeter of high reading accuracy which is provided outside of the apparatus. The colorimeter which is provided outside of the apparatus can adjust the absolute density by reading the color sample which is printed in advance by an exclusive printing apparatus which can perform high definition printing, the absolute density being guaranteed in the color sample.
Traditionally, calibration of the colorimeter provided in an apparatus has not been carried out. In order to calibrate the colorimeter provided in an apparatus, a color sample which guarantees the absolute density needs to be read by the colorimeter. However, since a traditional image forming apparatus cannot form a color sample which guarantees the absolute density on a sheet, a color sample which guarantees the absolute density cannot be read by the colorimeter provided in the apparatus in a normal reading operation.
In view of the above, there is a method where a color sample which guarantees the absolute density is housed in a sheet feeding tray of an image forming apparatus. The color sample which guarantees the absolute density is passed through the colorimeter to make the colorimeter read the color sample. By using the above method, the absolute density in the colorimeter is calibrated without requiring a mechanism exclusively for the calibration.
However, in the method where the color sample is housed in a sheet feeding tray of the image forming apparatus and passed through the colorimeter, the color sample passes through the conveying path which is used for the image forming process in the image forming apparatus. Therefore, the surface condition of the color sample may change due to wax and the like attaching thereto when passing though the fixer. There is a problem that this can cause a negative influence on the calibration.
Further, in the case where the color sample is conveyed according to a normal image forming process, the color sample may be deteriorated due to the conveying operation which is similar to that of when carrying out the image forming, and there is a problem that the color sample cannot be reused repeatedly.